ECE 453 Introduction to Computer Networks Lecture 11
- Slides: 13
ECE 453 – Introduction to Computer Networks Lecture 11 – Network Layer III – IP Protocol 1
Recap Network core: packet switching vs. circuit switching Network service: connectionless n n Best effort, no guarantee Datagram subnet Adaptive Routing n n n Decentralized routing (distance vector routing) Global routing (link state routing) Hierarchical routing Internet routing n n Intra-domain routing (OSPF, RIP) Inter-domain routing (BGP) 2
Names, Addresses, Route Name: identify what an object is Address: identify where it is Route: tell how to get there Each host on a TCP/IP internet is assigned a unique 32 -bit binary address (IPv 4) for computation and is used in all communications with that host 3
Internet Addressing Authority The Internet Corporation for Assigned Names and Numbers (ICANN) has ultimate control over number assigned n n Allocate IP addresses Manage DNS root servers 4
Hierarchy Within IP Address netid hostid Dotted decimal notation 10000001010 00000010 00011110 is written as 128. 10. 2. 30 One address for one host? 5
Implement Hierarchy of IP Address 01234 Class A 0 Class B 1 0 Class C 1 1 0 Class D 1 1 1 0 Class E 1 1 0 8 16 netid 24 31 hostid netid hostid Multicast address Reserved for future use Class Lowest address Highest address A 0. 1. 0. 0 126. 0. 0. 0 B 128. 0. 0. 0 191. 255. 0. 0 C 192. 0. 1. 0 223. 255. 0 D 224. 0. 0. 0 239. 255 E 240. 0 247. 255 6
Zero means this, One means All 7
Subnet: Extension to Addressing Network 128. 10. 1. 0 All traffic to 128. 10. 0. 0 128. 10. 1. 1 H 1 Rest of the Internet 128. 10. 1. 2 H 2 R Network 128. 10. 2. 0 128. 10. 2. 1 Internet part Local part Physical network Host H 3 128. 10. 2. 2 H 4 8
Subnet Implementation With Mask Network mask specifies how to partition local port of IP address into physical net and host port 11111111 0000 255. 0 specifies first three octets as network portion of the address 9
Classless Internet Address To divide an IP address at an arbitrary boundary Address masks n n Use (A, M) pairs in routing table, given a destination address D A = (D & M) E. g. 128. 10. 0. 0/16 RFC 1519, 1518 (CIDR) 10
Special IP Addresses single-network broadcast address: n 255 unconfigured address: n 0. 0 loopback address: n 127. X. X. X, typically 127. 0. 0. 1 private internets: n n n 10. 0. 0. 1 through 10. 255. 254 (10/8) 172. 16. 0. 1 through 172. 31. 255. 254 (172. 16/12) 192. 168. 0. 1 through 192. 168. 255. 254 (192. 168/16) 11
Assigning Addresses Manual configuration (fixed IP address) n n /etc/resolv. conf (name server) /etc/sysconfig/network (gateway) /etc/network-scripts/ifcfg-eth 0 (IP address, netmask, network) Control-panel Dynamic host configuration protocol (DHCP) n n DHCP server Client obtains an IP address dynamically 12
Examples IPADDR=160. 36. 30. 108 NETMASK=255. 254. 0 NETWORK=160. 36. 30. 0 BROADCAST=160. 36. 31. 255 13
